I found some time to work on haproxy last weeks and to perform a
number of

fundamental changes that have been needed for a long time.

[snipp]

Some of these changes conflicted with the ACL and pattern frameworks,
so it

was the right moment to merge them together. We now have a single
sample fetch

function for each type of data we want to extract, and both ACLs and
patterns
rely on this. The first user-visible benefit from this is that ACLs
can now

match cookies, URL parameters and arbitrary payloads. In practice,
the current

code is almost ready to enable session tracking on any input
criteria. I
thought I could make the track-sc1 and track-sc2 actions track
headers but

some more changes were needed that were out of the scope of all these
changes,
so I left them for later.
Since some ACLs and pattern fetch methods supported an argument, a
new argument

management framework was implemented, making it very easy to declare
variable
number of typed arguments for new keywords. Thanks to this extension,
I could
bring new optional arguments to hdr() and cook() fetch methods to
specify an
occurrence number. This allows stick-tables to extract an IP address
from a
precise occurrence of the X-Forwarded-For header for instance, and to
write

ACLs which match such headers against networks found in files.

[snipp]

After all this changes is it still necessary to have the appsession
directive in haproxy?

Could it not be removed to avoid confusions and future question what
should be used appsession